The present study aimed to evaluate the influence of Gluconacetobacter diazotrophicus (PAL5), Herbaspirillum seropedicae (HRC54) and Herbaspirillum rubrisubalbicans (HCC103) on seedling vigor, plant-crop productivity and potential to control the sugarcane Ratoon Stunting Disease (RSD) caused by Leifsonia xyli subsp. xyli (Lxx). Micropropagated seedlings (variety Co 421) were inoculated with endophytic diazotrophic bacteria and transplanted to the nursery. Lxx was inoculated in seedlings 80 days before field planting (seven months) by pruning the basal leaves with scissors pre-immersed in contaminated sap. To estimate diazotrophic bacteria's population density, shoot and root samples of seedlings transplanted to the nursery were collected at 42 and 86 days after inoculation. Agronomic characteristics of sugarcane plants were evaluated at harvest (16 months). In general, there was a population reduction of the bacterial endophytes after 86 days, compared to 42 days after inoculation. G. diazotrophicus provided greater gains in tons of cane per hectare (TCH) (68.6%) and tons of Brix per hectare (59.1%) than the other treatments. Plants inoculated with diazotrophic bacteria and challenged with the pathogen (Lxx) showed a high incidence of Lxx seropositive in the stalks. However, an increase in yield of 18.83 and 19.09 TCH was noticed, respectively, related to control and Lxx inoculated treatment in the first harvest (or growing season). The treatment with H. rubrisubalbicans alone showed a low incidence of Lxx and positive agronomic yield performance, suggesting some effect on the xylem pathogen colonization for the variety Co 421.

本研究旨在评估固氮葡萄糖酸醋杆菌(PAL5)、血清草螺旋菌(HRC54) 和红球草螺旋菌(HCC103) 对幼苗活力、植物作物生产力的影响以及控制由Lessonia引起的甘蔗宿根发育迟缓病 (RSD) 的潜力亚种 木木(Lxx)。微繁殖的幼苗（Co 421 品种）接种内生固氮菌并移植到苗圃。在大田种植前 80 天（七个月），通过用预先浸入受污染树液中的剪刀修剪基叶，将 Lxx 接种到幼苗中。为了估计固氮菌的种群密度，在接种后 42 天和 86 天收集移植到苗圃的幼苗的芽和根样本。在收获时（16 个月）评估甘蔗植物的农艺特性。一般而言，与接种后 42 天相比，86 天后细菌内生菌数量减少。固氮菌与其他处理相比，每公顷甘蔗吨数 (TCH) (68.6%) 和每公顷白利糖度 (59.1%) 的收益更大。用固氮菌接种并用病原体 (Lxx) 攻击的植物在茎中显示出高发生率的 Lxx 血清阳性。然而，注意到产量分别增加了 18.83 和 19.09 TCH，这与第一次收获（或生长季节）中的对照和 Lxx 接种处理有关。单独用H. rubrisubalbicans处理显示出Lxx发生率低和农艺产量表现积极，表明对品种 Co 421 的木质部病原体定植有一些影响。